Cam phaser for double camshaft

ABSTRACT

A cam phaser for a double camshaft, the cam phaser comprising: a rotor; and a stator, wherein the rotor is a rotatable relative to the stator about a rotor axis of the rotor that is coaxial to a longitudinal axis of the stator, wherein a radial vane of the rotor is positionable between two bars of the stator, wherein the radial vane divides an intermediary space formed between the two bars into two pressure cavities, wherein the double camshaft includes a first camshaft that is configured as a hollow cylinder and a second camshaft that is at least partially received in the first camshaft wherein the first camshaft and the second camshaft are rotatable relative to each other, wherein one of the first camshaft and the second camshaft is connected torque proof with the rotor and another of the first camshaft and the second camshaft is connected torque proof with the stator, wherein the rotor is movable by pressures in the two pressure chambers to cause a rotation of the first camshaft and the second camshaft relative to each other, wherein a hydraulic valve is arranged concentric to the first camshaft, the second camshaft and the rotor, and wherein the hydraulic valve is arranged axially between the second camshaft and the rotor.

RELATED APPLICATIONS

This application claims priority from and incorporates by reference German patent application DE 10 2020 109 328.4 filed on Apr. 3, 2020.

FIELD OF THE INVENTION

The invention relates to a cam phaser for a double camshaft, a camshaft arrangement and a hydraulic system.

BACKGROUND OF THE INVENTION

Cam phasers are being used in modern internal combustion engines for optimizing power and fuel burn by adjusting timing of gas control valves in order to be able to variably adjust a phase relationship between a crank shaft and a camshaft in a defined angular range. For this purpose, the cam phaser is integrated and received in a coupling device that facilitates transferring torques from the crank shaft to the camshaft. The cam phaser includes a rotor and a stator that are coaxially arranged relative to each other, wherein the stator radially envelops the rotor. Between the rotor and the stator chambers are provided that are loadable by a hydraulic fluid wherein the chambers are divided into counter acting pressure cavities by rotor vanes associated with the rotor. During operations of the internal combustion engine, both pressure cavities are permanently filled with the hydraulic fluid which provides a rather rigid connection between the rotor and the stator. Valve timing of the gas control valves is adjusted by increasing pressure in one of the pressure cavities while reducing pressure in the respective other pressure cavity. Thus, the hydraulic fluid has to be fed to one pressure cavity and drained from the other pressure cavity into a tank which changes the angular relationship between the camshaft and the crank shaft.

The patent document DE 10 2012 105 284 B4 discloses a cam phaser for a double camshaft wherein a rotor is supported in a predetermined angular position relative to the stator using a preload element configured as a coil spring. The double camshaft includes an inner camshaft which is at least partially enveloped by an outer camshaft. The outer camshaft is connected with the stator and the inner is connected with the rotor. A compensation element is provided in order to compensate tolerance induced offsets and/or parallel alignment deviations between the inner camshaft and the outer camshaft and the rotor. Thus, relative movements occur under friction between opposite components that lead to increased wear and heat development which limits the service life of the cam phaser with the double camshaft.

U.S. Pat. No. 9,909,463 published as US 2016/0230612 A1 owned by Applicant is incorporated in its entirety by this reference shows the structure of a cam phase stator and rotor with radial vanes.

BRIEF SUMMARY OF THE INVENTION

Thus, it is an object of the invention to provide a cam phaser for a double camshaft that provides an increased service life compared to a prior art cam phaser for a double camshaft. It is another object of the invention to provide a camshaft arrangement with increased service life and an advantageous hydraulic system. The object is achieved by A cam phaser for a double camshaft, the cam phaser comprising: a rotor; and a stator, wherein the rotor is a rotatable relative to the stator about a rotor axis of the rotor that is coaxial to a longitudinal axis of the stator, wherein a radial vane of the rotor is positionable between two bars of the stator, wherein the radial vane divides an intermediary space formed between the two bars into two pressure cavities, wherein the double camshaft includes a first camshaft that is configured as a hollow cylinder and a second camshaft that is at least partially received in the first camshaft wherein the first camshaft and the second camshaft are rotatable relative to each other, wherein one of the first camshaft and the second camshaft is connected torque proof with the rotor and another of the first camshaft and the second camshaft is connected torque proof with the stator, wherein the rotor is movable by pressures in the two pressure chambers to cause a rotation of the first camshaft and the second camshaft relative to each other, wherein a hydraulic valve is arranged concentric to the first camshaft, the second camshaft and the rotor, and wherein the hydraulic valve is arranged axially between the second camshaft and the rotor. Advantageous embodiments and advantages of the invention can be derived from the dependent claims, the description, and the drawing FIGURE.

The invention proposes a cam phaser for a double camshaft, the cam phaser comprising a rotor and a stator. The rotor is a rotatable relative to the stator about a rotor axis of the rotor that is coaxial to a longitudinal axis of the stator. A vane of the rotor is positionable between two bars of the stator, wherein the vane divides an intermediary space formed between two bars into two pressure cavities. The double camshaft includes a first camshaft that is configured as a hollow cylinder and a second camshaft that is at least partially received in the first camshaft wherein the first camshaft and the second camshaft are rotatable relative to each other. One of the two camshafts is connected with the rotor and the other of the other two camshafts is connected with the stator. The rotor is movable by pressures in the pressure chamber in order to provide relative rotation to the double camshaft. According to the invention a hydraulic valve is arranged concentric to the camshafts and the rotor in an axial direction between the second camshaft and the rotor. The advantage of the invention is position stabilization of the inner camshaft which is designated as the second camshaft. The inner camshaft is arranged axially adjacent to the hydraulic valve. In order to provide reliable positioning, the hydraulic valve or a face of the hydraulic valve oriented towards the inner camshaft can have a ring which engages a groove in the inner camshaft.

When the hydraulic valve is arranged in the first camshaft the hydraulic valve can also be used for radially positioning the first camshaft which is the outer camshaft according to the invention.

In another embodiment of the invention the hydraulic valve is flow connected with a camshaft bearing of the double camshaft. Advantageously hydraulic fluid can be used for flowing the cam phaser from a lubrication system of an internal combustion engine that includes the cam phaser according to the invention and the double camshaft so that a second lubrication system configured as a hydraulic fluid system is not required anymore which reduces the cost of the cam phaser.

Advantageously, a coupling, in particular configured as an Oldham coupling can be arranged between the second camshaft and the hydraulic valve. Thus offsets in axial and radial direction and angular alignment errors between the first camshaft and the second camshaft can be compensated in a simple manner.

In order to keep friction, and thus wear and heat generation due to the friction, small between components adjacent to the coupling and the coupling itself during operation of the cam phaser the hydraulic valve is configured to provide lubricant to the coupling and/or the double camshaft. This means put differently that the hydraulic valve is configured to conduct lubricant or hydraulic fluid to the coupling and/or the double camshaft.

In another an advantageous embodiment the hydraulic valve includes a flowable opening at a face that is oriented towards the coupling in order to provide hydraulic fluid conduction. Thus, hydraulic fluid can be fed from the hydraulic valve through the opening of the coupling or can flow through the opening to the coupling wherein the hydraulic fluid can be the lubricant of the internal combustion engine.

In order to be able to produce the opening in a simple manner the opening is configured in a terminal cover of the hydraulic valve. Typically, the hydraulic valve is made from a hollow cylindrical bushing that receives an axially moveable piston in its cavity. In order to produce the bushing in a simple manner the cavity is configured as a borehole so that the bushing is open at both ends. The piston is inserted into the cavity and protrudes at one of the two ends beyond the bushing in order to be actuated by an actuator. The other end is typically at least substantially closed by a terminal cover. The opening can be introduced into the terminal cover in order to provide lubricant to the coupling wherein the opening is in particular provided as a borehole for reasons of cost-effective fabrication.

In another advantageous embodiment of the cam phaser according to the invention a coupling element of the coupling includes a flow through channel. Thus, lubricant fed from the hydraulic valve to the coupling can be distributed in the coupling itself, in particular the lubricant can be conducted to a side of the coupling that is oriented away from the hydraulic valve and that is configured opposite to the inner camshaft. Thus, in addition to the ability to provide contacting surfaces of the inner camshaft and the coupling with lubricant there is the option to supply a movement gap with lubricant through the inner camshaft wherein the movement gap is arranged between the inner camshaft and the outer camshaft, wherein the sleeve shaped movement gap is required to move the two camshafts relative to each other since the inner camshaft is received in the outer camshaft.

Another aspect of the invention relates to a camshaft arrangement comprising of a first camshaft and a second camshaft wherein the second camshaft is rotatably received in the first camshaft. The camshafts are rotatable relative to each other by a cam phaser that is configured according to one of the claims 1-9. Advantages of the camshaft arrangement according to the invention are reduced installation space and reduced fabrication cost since the cam phaser helps to reduce fabrication cost.

A third aspect of the invention relates to a hydraulic system which includes a cam phaser and a hydraulic valve that hydraulically loads the cam phaser wherein the hydraulic valve is advantageously configured as a central valve which is also designated as central bolt.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention can be derived from the subsequent drawing description. The drawing FIGURE illustrates embodiments of the invention. The drawing, the description and the claims include several features in combination. A person skilled in the art will also view these features individually and combine them into useful additional combinations. The drawing FIGURE illustrates a cam phaser according to the invention in a longitudinal sectional view.

DETAILED DESCRIPTION OF THE INVENTION

The drawing FIGURE illustrates one of many possible embodiments of the invention and does not limit the spirit and scope of the invention.

The cam phaser 10 according to the invention for a double camshaft 12 is configured according to the drawing FIGURE. The cam phaser 10 forms a camshaft arrangement 14 together with the double camshaft 12.

The cam phaser 10 adjusts an angular relationship between a crankshaft of the internal combustion engine and the double camshaft 12 or one of two concentric camshafts of the double camshaft 12, a first camshaft 16, and a second camshaft 18 during operations of the internal combustion engine. Internal rotation of the double camshaft 12 adjusts opening and closing timing of gas control valves of the internal combustion engine so that the internal combustion engine delivers optimum power at a respective speed. The cam phaser 10 facilitates continuous adjustment of the double camshaft 12 relative to the crankshaft.

The first camshaft 16 is configured hollow cylindrical and receives the second camshaft 18 in its cavity 20. The second camshaft 18 is also configured hollow cylindrical but also could be configured solid. The two camshafts 16, 18, are configured coaxial and rotatable relative to each other about a rotation axis 22 within limits. The rotation of the two camshafts 16, 18 relative to each other causes a phase adjustment of the intake and/or exhaust timing.

The cam phaser 10 includes a stator 24 with a longitudinal axis 26 with a rotor 28 with a rotor axis 30, wherein the rotor 28 is rotatable relative to the stator 24 about the rotation axis 30 that is configured coaxial with the longitudinal axis 26.

The stator 24 is connected torque proof with an operating element 32 that provides a connection between the double camshaft 12 and the crankshaft wherein the operating element 32 is configured e.g. as a sprocket. A timing chain configured as a drive element can be run over the sprocket 32 so that the stator 24 is operatively connected with the crankshaft. By the same token, the operating element 32 can be a timing belt cog wherein a timing belt is run over the timing belt cog as a drive element.

The stator 24 that is connected torque proof with the first camshaft 16 includes radially inward protruding bars 34. Vanes of the rotor 28 are respectively arranged distributed over the circumference between the bars 34. The vanes of the rotor 28 are attached at a rotor hub 36 that is connected to torque proof with the second camshaft 18. Thus, the rotor hub 36 is connected with a hydraulic valve 38 configured as a central valve. Thus, a hydraulic system 40 that includes a cam phaser 10 and the hydraulic valve 38 is provided.

Pressure chambers 42 that are loadable with a hydraulic fluid are arranged between the rotor 28 and the stator 24 wherein the pressure chambers are divided by the vanes into counteracting pressure cavities 42 wherein the hydraulic fluid loads the pressure chambers 42 through pass through openings 44 configured in the rotor hub 36 in a manner that is controlled by the hydraulic valve 38. In order to form pressure chambers 42 that are sealed relative to ambient covers 46 that define the pressure chambers 42 in the axial direction are arranged on both sides of the stator 24 and the rotor 28.

During operations of the internal combustion engine the pressure chambers 42 are continuously filled with hydraulic fluid so that the rotor 28 and the stator 24 are connected with each other in a rather rigid manner. In order to adjust an angular position of the double camshaft 12 relative to the crankshaft the rotor 28 is rotated relative to the stator 24. Thus, the pressure chambers 42 are loaded or unloaded by feeding hydraulic fluid or draining the hydraulic fluid into a tank depending on a desired direction of rotation.

In the illustrated embodiment cams configured as outlet cams are associated with the first camshaft 16 and cams 48 configured as inlet cams are associated with the second camshaft 18. Since the second camshaft 18 is configured as an inner camshaft of the double camshaft 12 it's cams 48 include a shaft receiving opening 50 to receive the first camshaft 16, wherein the first camshaft 16 is rotatable in the shaft receiving opening 50. In order for the cam 48 to follow the rotation of the second camshaft 18 the cam 48 is connected torque proof with the second camshaft 18 by a bolt 50.

In order to facilitate an unimpeded loading of the gas control valve configured as an inlet valve by the cam 48 the cam 48 includes a hollow cylindrical sleeve section 54 with a pass through opening 56 wherein the bolt 52 is inserted into the pass through opening 56 in order to provide the torque proof connection with the second camshaft 18. This means put differently that the bolt 52 is fixed at the sleeve section 54 and thus at the cam 48 as well as at the second camshaft 18.

It is appreciated that the first camshaft 16 may have cams configured as exhaust cams corresponding to a number of exhaust valves. Thus, it is appreciated that the second camshaft 18 may have cams 48 configured as inlet cams corresponding to a number of inlet valves. By the same token the first camshaft 16 can have cams configured as inlet cams to actuate the inlet valves and the second camshaft 18 may have cams configured to actuate the outlet valves. The double camshaft 12 can be configured to actuate outlet valves exclusively or inlet valves exclusively.

In order to control a position between the stator 24 and the rotor 28 that is required for starting the internal combustion engine a preload element is provided that rotates the rotor 28 into a correct position relative to the stator. This means put differently that the rotor 28 is preloaded relative to the stator 24. A fixing of the correct position is implemented by a locking device that is loadable by the hydraulic valve 38 to engage or disengage the fixing.

The hydraulic valve 38 that is configured to control at least the cam phaser 10 includes a hollow cylindrical bushing 58 that is configured to moveably receive a piston 60. The piston 60 is configured to move axially in a direction of the longitudinal axis 26 and operatively connected with an actuator through a plunger 63. Control edges 66 formed at an enveloping surface 64 of the plunger open or close bushing openings configured in the bushings 58 for flow through, wherein the bushing openings 68 are flow connected with operating connects A, B and at least one tank connection T and a supply connection P. The piston 60 is configured hollow to provide flow through.

A terminal cover 70 is arranged at an end of the bushing 58 that is oriented away from the plunger 63 wherein the terminal cover provides secure reception of a reset element 72 to preload and position the piston 60.

A coupling 74 including a disc shaped coupling element 76 is configured between the bushing 58 and the second camshaft 18. The coupling is configured as an Oldham coupling and eliminates or at least reduces axial offsets of the components to be connected, in the instant embodiment the second camshaft and the bushing 58.

It Is appreciated that the coupling 74 compensates wear generated during operations and fabrication tolerances which causes misalignments in radially direction, axially direction and angular misalignments.

A first phase 78 of the hydraulic valve 38 configured towards the coupling element 76 is configured as the Oldham coupling 74 in order to provide a form locking connection with the coupling element. By the same token a second phase 80 of the second camshaft 18 is configured to provide a form locking connection with the coupling element 76 configured as the Oldham coupling 74 wherein the second phase 80 is oriented towards the coupling element 76. In the instant embodiment the coupling 74 is configured to connect the components through a groove-key connection. By the same token connection elements can be configured between the components 15, 58, and the coupling element 76 to provide a form locking connection.

The two camshafts 16,18 are provided with lubricant through a camshaft bearing 88 that is proximal to the cam phaser 10 and that is provided with the lubricant from a feed pump through the regular lubricant cycle of the internal combustion engine. Thus, the first camshaft 16 includes a lubricant opening 90 that penetrates an entirety of the camshaft in a radial direction.

In order to reduce wear of the coupling 70 a lubricant supply is provided wherein the lubricant is supplied through the hydraulic valve 38. The lubricant flowing through the lubricant opening 90 flows through a bushing supply opening 92 that is associated with the supply connection P that includes a sieve 94 and a check valve 96 so that the lubricant flows into an annular groove 98 configured at the piston 60. Since the sieve 94 is configured to capture particles in the lubricant the lubricant can be used as a hydraulic fluid.

The hydraulic fluid flows from the ring groove 98 according to the flow line provided with an arrow through an annular gap 100 configured between the piston 60 and the bushing 58 into the hollow cylindrical terminal cover 70 in order to flow from there into a cover opening 82 formed in the terminal cover 70 to flow about the coupling element 76 and flow between the coupling element 76 and the first face 78. By the same token the hydraulic fluid can flow between the key-groove gaps that are typical for the Oldham coupling as illustrated in an exemplary manner by the dashed flowline.

The coupling element 76 includes a flow channel 84 through which the hydraulic fluid can move through the coupling element 76 between the second face 80 and the coupling element 76. By the same token the hydraulic fluid can move between the first camshaft 16 and the second camshaft 18 so that additional lubrication can be provided. Thus all opposing surfaces of the coupling element 76 and of the hydraulic valve 38 and of the second camshaft 18 can be provided with lubricant which substantially reduces wear since solid body contact friction is avoided or at least reduced.

In order for hydraulic fluid flowing through the cover opening 82 not to impair the adjustment of the cam phaser the piston 60 is closed at a third face 86 that is oriented towards the reset element 72 wherein the closure is provided in the instant embodiment by a cylinder 102. A second lubricant opening 104 that is configured in the first camshaft 16 provides draining of the hydraulic fluid. 

What is claimed is:
 1. A cam phaser for a double camshaft, the cam phaser comprising: a rotor; and a stator, wherein the rotor is a rotatable relative to the stator about a rotor axis of the rotor that is coaxial to a longitudinal axis of the stator, wherein a radial vane of the rotor is positionable between two bars of the stator, wherein the radial vane divides an intermediary space formed between the two bars into two pressure cavities, wherein the double camshaft includes a first camshaft that is configured as a hollow cylinder and a second camshaft that is at least partially received in the first camshaft wherein the first camshaft and the second camshaft are rotatable relative to each other, wherein one of the first camshaft and the second camshaft is connected torque proof with the rotor and another of the first camshaft and the second camshaft is connected torque proof with the stator, wherein the rotor is movable by pressures in the two pressure chambers to cause a rotation of the first camshaft and the second camshaft relative to each other, wherein a hydraulic valve is arranged concentric to the first camshaft, the second camshaft and the rotor, and wherein the hydraulic valve is arranged axially between the second camshaft and the rotor.
 2. The cam phaser according to claim 1, wherein the hydraulic valve is arranged within the first camshaft.
 3. The cam phaser according to claim 1, wherein the hydraulic valve is flow connected with a camshaft bearing of the double camshaft.
 4. The cam phaser according to preceding claim 1, wherein a coupling is arranged between the second camshaft and the hydraulic valve.
 5. The cam phaser according to claim 4, wherein the hydraulic valve is configured to provide the coupling or the double camshaft with lubricant.
 6. The cam phaser according to claim 5, wherein the hydraulic valve includes a flowable opening at a face that is oriented towards the coupling.
 7. The cam phaser according to claim 6, wherein the opening is configured in a terminal cover of the hydraulic valve.
 8. The cam phaser according to claim 7, wherein the opening is configured as a borehole.
 9. The cam phaser according to claim 4, wherein a coupling element of the coupling includes a flowable flow channel.
 10. A camshaft arrangement, comprising: a first camshaft and a second camshaft, wherein the second camshaft is rotatably received in the first camshaft, and wherein the first camshaft and the second camshaft are rotatable relative to each other by the cam phaser according to claim
 1. 11. A hydraulic system, comprising: the cam phaser according to claim 1; and a hydraulic valve configured as a central valve. 